Process for the manufacture of porous flexible sheet material



Dec. 18, 1956 C. L. NOTTEBOHM ET AL 2,774,687 PROCESS FOR THEMANUEACTURE 0F POROUS FLEXIBLE SHEET MATERIAL Filed Sept. l. 195356,9006 fla-Q Wap/m76.

PROCESS FOR THE MANUFACTURE OF POROUSv FLEXIBLE SHEET MATERIAL CarlLudwig Nottebohm, Weinheim an der Bergstrasse, l

Germany, Werner Jacob, Lowell, Mass., and Wilhelm' Lauppe and RobertSchabert, Weinheim an der Bergstrasse, Germany Application September 1,1953, Serial No. 377,979

Claims priority, application Germany September 3, 1952 9 Claims. (Cl.117-120) The present invention relates to the manufacture of porous,flexible sheet material similar to textile or leather which involvesimpregnating` ber eeces with lm-forming binders, preferably emulsions ordispersions ofv examples, may be mentioned vegetable bers, such V ascotton, ramie, ax, jute,.animal bers, such as wool and j other animalhair or human hair, or synthetic bers, such as viscose bers, acetatebers, superpolyamide bers, polyvinyl bers, polyvinylidene bers,polyethylene bers,

polyester bers, lPolyacryl bers, bers consisting of co-V polymers ofseveral ber-forming monomeric compounds, protein bers, alginate bers,casein bers, mineral bers,

United States Patent such as glassor stone-wool or asbestos bers, ormix- .l

tures of two or more of the above mentioned types of bers. It isessential that the bers are used in cardable 8 cm., preferably about 2to 6 cm. Fibers such as horsehair, cocoanut bers, etc. which are toolong or too thick and which have hard and smooth surfaces, renderingthem unsuitable for carding on ordinary carding machines have generallybeen found unsuitable for use in processesk of..

the type in question.

Suitable binders are, as mentioned heretofore, preferably emulsions ordispersions of natural and/-or synthetic rubber. Excellent results havebeen obtained, for instance, with polymers of butadiene-acrylonitrile,butadiene-styrene, their derivatives, such as chloroprene,and theircopolymers.

additional components, such as wetting agents, dispersing agents,thickening agents, antioxidants, llers, vulcani'zing agents,vulcanization accelerators and the like. The aqueous emulsions ordispersions may contain-about 15 Vto 35% by weight and preferably about20 'to 29% byl weight of solid binder, such as natural rubber. Wettingagents, such as sodium isobutylene naphthylene sulphonate (Nekal) may bepresent in an amount up to 60% by weight of the solid binder content ofthe dispersion. Preferably about 20 to 28 parts by solid weightof'wetting agents are used for each 100 parts by weight of bindersolids. ployed in the rubber industry, such as, for instance,paraphenylenediamine derivatives, mercapto benzamidazol or The emulsionsor dispersions vused for impregnating the ber fleece may contain one ormore.`

The antioxidants used are those commonly ern-l form.` 'Iheir lengthshould be generally about 0.8 to .40

2,774,687 n Patented Dec. 18, 1956 phenyl beta-naphthylamine. Apreferred method of manufacturing brous sheet material, as described inthe above mentioned copending applications comprises the followingsteps:

T-he bers or ber mixtures, which may rst have been verse rdircti'om*'thethin webs, the bers of which havey been partially aligned inlongitudinal direction by4 the carding o'peratiom are Aplaced uponv oneanother at an angle inv'such a manner that the bers of adjacent layerscrosseach 'other and, thus, a eece is formed in which the' bers extendin various directions, i. e., the bers are v polyposed.` In order toobtain an intimate cohesion be--v tween thesuperposed websv and toproduce a light felting, increased densen'es's yand smooth surfaces, themulti-layer eeces are passed through pressure rollers heated to abouteece, for instance,` by spraying -or by means of rollers? Advantageouslythe binder liquid is spreadonl the surface of the eece in the form of astili foam havinga high air "content When the eece is dried, its surfacebers are cemented together at their crossing points undertpreservationof practically all the interstices between the bers rand the surface-ofthe fleece is coated with athin, spider-web like net of binder. Thisunilateral surface treatmentstabilizes the fleece sufficiently to permitits through impregnation, for instance by passing it through rollerpairs, without dangerof the eece being torn'orserious distorted. n

The unilaterally stabilized eece is now' through impregnated by passingit through a pair of rollers having their axes disposed in a horizontalplane whilev a suitable lm-formingfbinder liquid is pressed through itsuntreated surface uniformly in such 'a' manner that it penetratesthe-entire thickness of the eece.

stepgin-the formofa stableowable foam.

`The impregnated eece or sheetmaterial is driedfor instance, by passingit through a drying chamber heated to about to '120 C. yThis dryingstepmay 'also involve avulcanization or-nal vulcanization of therubberbinder. After-drying, the material may vbe subjected to, the

usual after-treatments, such as calendering, washing, etc.

Subsequent to calendering, nal vulcanization may be effected,for-instance, by heating the material to temperatures of C.' or higher.Dependent upon the typey and composition of the brous material, the typeand composition Aofv the binder, the quantity proportions between brousmaterial and binder and the specic' conditions under'which theimpregnation is carried out, products can be obtained which have theproperties desi-red for the particular purpose for which the material`is intended, such as softness, porosity, elasticity, springiness,creaseresistance, water resistance, and fastness against washing'andcleaning. The material may also be treated -in such away that it can bestitched, padded orsewedon:V

The binderl liquid is preferably used in the through impregnating' 3sewing machines, and it can be dyed any desired color.

The quantity of the film-forming binder material introduced into thefiber fieece is, preferably, so selected that the fibers are cementedtogether at their crossing points only and such interstices or pores.are maintained that porous structures are formed which are similar totextiles. Generally, it has been found advantageous to produce sheetmaterial containing about 25 to about 65 percent by weight and,(preferably about 35 to 55% by Weight) of solid binder particles .andabout 75` to 35% by weight of fibrous material. The finished sheetmaterial has a thickness of about 0.15 to 1.5 millimeter and,preferably, ofabout 0.2 to 0.9 millimeter. It is soft, 1iexible and hasa textile-like feel and drape', uniformpor'osity and excellentelasticity. lAs compared to ordinary textile fabrics, which havedifferent properties in'the direction of the Woof and of ythe warp,sheet materials prepared by the described process are distinguished byiso-elasticity; that is, they are `resiliently and uniformly resistantto creasing'or folding in'any direction.

If the described process' is usedfor themanufacture of form-'giving andform-retaining"interlinirigs or stiiening materials or as `coldan'dldust protecting interlinings for clothing, it is preferred to usefiber'fieeces which contain wool, possibly mixed with other fibers andtoftreat such flee'ces with aqueous dispersions or emulsions of naturalor synthetic rubber containing vulcanizing agents, vulcanizationaccelerators, wetting agents and Aantioxidants. After impregnation, theproducts are vulcanized, then freed of water-soluble components bywashing and finally dried.I The fiber eeces used for these purposesshould generally contain at least by Weight, and preferably fromv to 70%by weight, of wool fibers.

Binder liquids which are preferred for use in the described process areemulsions or dispersions of synthetic rubbers or mixtures thereof,therDefo values of which in dry condition .are between 1000 and 8000degrees Defo. As will be understood by those familiar with the art, theterm Defo hardness designates the force in grams which is required tocompress a rubber test cylinder of 10 millimeterI height and 10millimeter diameter at l80v C. in thirtyseconds by 4 millimeter (compareHouwink, page 450). The Defo values determine the` degree of softnessand the Idegree of elasticity of the rubber.

For the preparation of softer, still fabric-like products of lessspringiness, fiber mixtures may be used 'which do not contain `any woolfibers. Thus, a fleece made from a mixture of 30 parts by Weight ofpolyamide fiber', 30 parts by weight o'f cell wool acetate fiber, 20parts by weight of ramie fiber combings and 20 parts by weight of cellwool viscose fiber may be impregnated withv a soft, synthetic rubber(Defo valueA between about 800 and 1700).

In some cases it is advantageous to'incorporate into. the fibrous sheetmaterial'water repellant lubricants, such as p'arafiin, wax or the likein quantities of about 2 to 10% by weight. These materials act duringsewing, especially sewing on sewing machines, as lubricants for theneedles. The waterrepe'llant lubricants can be used in combination withother water repellant materials, such as aluminum salts; preferably theWater repellant lubricants or other water -repellants are incorporatedinto the solidified and vulcanize'd'sheet material after washingthereof.

While' the products obtainable by the heretofore describedmethods; asparticularly set forth and disclosed in the applicants above mentionedcopendingpatent applications, produce valuable sheet material havingoutstanding properties with regard to porosity, elasticity,springiness,l etc., it has now been found that the products can befur-ther improved, particularly as regards' their springiness, theirfastness against dry cleaning and their abrasion resistance. It is theprincipal objectv of4 4 the present invention to provide methods forattaining such improvements.

In order to accomplish this object, it is proposed, according to thepresent invention, to incorporate into the fiber fieeces in addition tothe above mentioned filmforming binders and previously specifiedadditional cornponents, such as vulcanizing agents, vulcanizationaccelerators, fillers, water repellants, etc., certain relatively smallquantities of synthetic resin condensates. Suitable Synthetic resincondensates are, for instance, condensates of aldehydes, and preferablycondensates of formaldehyde with substances which can be condensed withaldehydes, such as phenols `and derivatives thereof,

urea and urea compounds and derivatives, such as cyan` theirpre-condensates which are stillrsoluble in water.

Such water soluble pre-condensate may, forinstance, be'

admixed to `a rubber dispersion or emulsion which may also contain othercomponents, such as wetting agents, vulcanizing agents, vulcanizationaccelerators and the like, and this mixture may be used for the throughim'- pregnation of the fiber fleeces. It is preferred to incorporateinto the aqueous mixture' additional substances which are capable ofpromoting or accelerating the conversion of the condensation products totheir insoluble final state. Suitable condensation activators are, forinstance, alkali compositions,` such as caustic soda solution, earthalkali compositions, such as barium chloride, ammonium salts, such :asammonium chloride, organic acids, such as lactic acid and sulphonicacids or their salts, such as sodium lauryl sulphonate or soaps of the Itype obtainable from fatty acids plus ammonia. Sometimes, certaincomponents of the impregnating dispersion which are present for otherpurposes, such as vulcanizing agents, vulcanization accelerators,anti-oxidants or emulsifying agents may act as condensation activators.A material which can serve such double purpose is, for instance,hexamethylene tetrarnine.

The most -suitable quantities of poly-condensates to be used can beascertained by simple tests and ran-ge from about l-15% by weight of thebinder solids. In the manufacture of sheet material which is intended asinterlining for articles of clothing, the quantities of polycondensatesto be employed may be determined on the basis of the Defo values of therubbers used in the binder liquids, as shown by the following table:

Defo values of Rubber It has been found desirable to use the dispersionsorl emulsions which, according to the invention, contain, in"

addition to the rubber binders, also Water soluble precondensates ofsynthetic resins, such as pre-condensates' of formaldehyde with phenols,urea and thev like, in the in such a manner and quantity into/ theimpregnating binder dispersion that they do no't prevent the conversiono f the dispersion into a stable foam suitable for` impregnation vof thelieeces. For this reason, generally, according to the invention, onlyrelatively small quantities of water soluble precondensates of watersoluble compounds` capable of condensation are added to the impregnatingdispersions. In some cases, it-has also been found advantageous toincorporate into the fibrous eeces or into the impregnating dispersions,softening agents of the type generally used in thesynthetic resincondensate industry. Typical softening agents of this type are, forinstance, glycerine, glycols, fatty acid esters and the like.

The impregnation of the ber eeces may be carried out in the mannerdescribed above and set forth in detail in the applicants abovementioned co-pending applications by converting the impregnatingdispersion containing, in addition to the film-forming binders, alsoprecondensates of synthetic resins, such as formaldehyde with substancescondensable therewith, and possibly other desired components, to astable, owable foam and pressing this foam by means of rollers into theeeces. The stabilization of the impregnation may be eiected by heatagglomeration such as, for instance, simple drying. For this purpose,the impregnated fleeces may be passed through heating chambers. Caremust be taken to carry out the after-treatment of the impregnated eecesunder such conditions that the precondensates are converted to theirWater insoluble and solvent resistant final form. In order to accomplishthis result, the drying and vulcanization steps may-be suitably modifiedwithV regard to the temperature and the duration of the heat treat.ment. According to one embodiment of the process according to theinvention, the impregnated sheet ma-v terial is subjected, after heatcoagulation, to a vulcanizing treatment at temperatures from about 80 to120 C. which is continued until complete vulcauization of the rubber andsimultaneous complete conversion of the synthetic resinv condensate toits final condensed state has taken place. Thereafter, the material maybe washed and subjected to any `other desired after treatment.

, The vulcanization and hardening of the synthetic resin condensates mayalso becarried out in several stages. Thus, the impregnated and driedmaterial may first be prevulcanized at temperatures of 80 to 95 C., thencalendered, washed and passed through a paraffin emulsion bath.Thereafter, the rubber components may be finally vulcanized and thesynthetic resin condensates may be converted to their final insolublestate or hardened by subjecting the impregnated sheet material for about24 hours to temperatures between 80 to 100 C. It will be understood thatthe heat treatments must` be carried out under such conditions that thefibers are not damaged. Generally, it is recommended to use temperaturesnot exceeding about 135 C.

Due to the incorporation of hardened condensation products of aldehydes,preferably formaldehyde, with substances which can be condensedtherewith, such as phenols, ureas, etc., the properties of the productsaccording to the invention are improved in various respects. Thus, theincorporation into a fiber fleece of a quantity of phenol formaldehydecondensate in an amount of about 4% by weight of the film formingelastic rubber solids constituting the primary binder leads to productshaving substantially improved springiness and abrasion resistance. Suchproducts are particularly suitable for use as interlinings in clothing.

lThe accompanying drawing shows several alternate procedures inaccordance with the present invention.

The following examples may serve to illustrate the invention.

' Example 1 A fiber mixture consisting of 30 parts by weight of cottoncombings, 30 parts by Weight of ramie combings and'40 parts by weight ofcell wool combings was formed into a fiber fleece havinga weight of 135g. per square millimeter. The vfleece was condensed and streachedbetween pressure rollers heated to C.

A stiff foam was formed from an aqueous dispersion of the followingcomposition:

The foam was spread uniformly in a very thin layer by means -of a doctorblade onto one lsurface of the fiber fleece while the eece was passedunder the blade, whereupon the eece was dried.

-The sheet material, stabilized by this unilateral pretreatment, was nowpassed between a pair of cooperating rollers with smooth surfaces havingtheir axes arranged in a horizontal plane, and a stable, flowableaqueous foam was pressed into the fleece through its untreated surface,so as to penetrate the cutive thickness of the lieece. The foam wasprepared from a dispersion of the following composition:

The mixture contained about 22.5% by Weight of the solution of rubbersolids and about 25.2% by weight of the solution of total solids.

The impregnated eece lwas now passed through a drying chamber where itwas dried at about to 100 C. for twenty minutes and simultaneouslypre-vulcanized. The resulting highly porous sheet material, whichalready exhibited good springiness, was now finally vulcanized andhardened for about twenty-four hours at 75 C. in a drying chamber.Thereafter, it was washed in a washing machine in the manner customaryin the textile industry whereby all water soluble `substances weredissolved out. Then, the material was dried again and treated withparafn-wax-aluminum salt dispersion to make it water repellant. Thefinal product had a thickness of .8 to 1 millimeter and a weight ofabout 220 g. per square millimeter. Its rubber content was labout 42% byweight. The material had the particular advantage that its propertieswere not significantly impaired by dry cleaning. lt exhibited excellentspringiness after dry cleaning.

Example 2 A mixture of 50 parts by weight of cotton combings and 50parts by weight of cell wool was formed into thin fibrous webs and anumber of these webs were superposed upon one another to produce a eececontaining bers disposed in all directions and having, after stretching,a weight of about 70 to 100 g. per square meter. One surface of thefleece was pretreated with a foam having the same composition as thepretreatment foam described in Example l.

VAfter drying, the unilaterally prestablized fleece was treated by meansof a pair of rollers, as described in Example gl, with a stable,flowable foam obtained from a dispersion of the following composition:

The impregnated material was treated with a saturated sodiumsulphatesolution and dried. Thereafter, it was subjected to a secondimpregnation by passing the sheet material through a pair of rollerswith smooth surfaces and pressing into both surfaces of the sheet anaqueous paste of the following composition:

Liquid Solid Parts Parts B. W. B. W.

Butadiene-acrylonitrile dispersion (37%) 270 100 Starch solution (35%)90 Sodiumsulphate 100 Sulphur dispersion (80 3 Zincoxide dispersion(50%) 12 6 Zinc salt of phcnylethyldithiocarbaminic acid as dispersion(25%) 4 1 Paraphenyldiamine derivative (25%) 8 2 After the secondimpregnation, the material was vulcanized by passing it over drying.cylinders at a temperature of about 110 C. and final vulcanization andhardening of the synthetic resin components was accomplished bysubsequent storing in a drying oven. Thereafter, the finally vulcanizedand hardened material was thoroughly washed in washing machines wherebyall water soluble components were dissolved out, leaving numerous fineand extra fine pores in the material. The material was then dried. ltwas characterized by extremely high porosity and absorptiveness.Generally, it had the properties of chamois leather, but, due to thepresence of the phenol-formaldehyde resin, its abrasion resistance wassubstantially greater than that ofnatural leather.

Further experiments have shown that in some cases it is advantageous tointroduce at least part of the synthetic resin condensates into thefibrous sheet material in a second impregnating stage following theimpregnation of the sheet material -with the elastic binders, such asnatural or synthetic rubber. In these cases, the fiber fleece is treatedin a first impregnating stage, preferably in the manner disclosed in theapplicants prior copending patent applications 262,941 and 262,942, witha dispersion or emulsion containing the film-forming binder andpreferably such additional materials, as wetting agents, vulcanizingagents, antioxidants and the like, and the pre-impregnated sheetmaterial thus obtained is then treated in a second impregnating stagewith at least one synthetic resin precondensate, such as a precondensateof an aldehyde with phenols, urea or urea derivatives. Finally, theimpregnated sheet material is subjected to a treatment suitable for thehardening of the synthetic resin condensate, for instance by heating inthe presence of condensation catalysts.

This two-stage process has the advantage that it permits theintroduction into the fibrous sheet material of such precondensateswhich are incompatible with one or more of the components of the binderliquids used for the principal impregnation of the fibrous material.Certain melamine resins are typical examples of this group of syntheticresins suitable for use in the second impregnating stage of a two-stageimpregnation. The secondary impregnation of the fibrous sheet materialpreimpregnated with film-forming binders may be carried out withemulsions, dispersions or solutions containing the synthetic resinprecondensate in crystalloid-dispersed form, in colloid-dispersed formor in hetero-dispersed form. Such emulsions, dispersions or solutionsmay, in addition to the precondensates used, also contain catalystscapable of promoting the conversion of the precondensates to theirinsoluble final state. Suitable condensation catalysts are, forinstance, ammonium salts, such as ammonium chloride, di-amrnoniurnphosphate or propanolaminehydrochloride, anorganic acids, such ashydrochloric acid or boric acid, anorganic bases, such as caustic sodasolution or ammonia and organic bases such as, for instance,triethanolamine. The secondary impregnation may, for instance, becarried out with phenolic plastics in their soluble state, such as, forinstance, the known precondensates of formaldehyde with urea or ureaderivatives known under the trade names Ka 1525 or GFT 167,

the urea precondensate known under the trade name- Kaurit KW or thedicyandiamide known under the trade name Kaurit DD. Other suitableprecondensates are known under the trade names Cassurit(trihydroxymethylmelamine), Lyotix MA (etheried trihydroxymethylmelamine), Lyofix CH (hexahydroxymethyl melamine) or Aerotex (etheriedhydroxymethyl melamine).

It is recommended to use such precondensates which, after hardening, areresistant to organic solvents, as they are used in dry cleaningoperations and which thus help to preserve the desired properties of theproducts, especially with regard to elasticity, springiness, feel, etc.,even after several dry cleanings. Condensation products of melamine withformaldehyde or other aldehydes have been found to be particularlysuitable for this purpose.

According to a further embodiment of the invention, the precondensatesto be introduced into the fibrous sheet material are used partly in thefirst impregnating stage as components of the emulsions or dispersionscontaining the film-forming binder and partly in the second impregnatingstage applied to the fibrous sheet material obtained from the firstimpregnating stage. It is possible to use in both impregnating stagesprecondensates of the same type, but, according to a preferred mode ofoperation, the first impregnating stage is carried out with emulsions ordispersions containing precondensates which are Well compatible with thefilm-forming binders and other components of the binder liquids employedin this stage, while in the second impregnating stage (finalimpregnation) precondensates are used which are more or lessincompatible with the components of the binder liquids used in the firstimpregnating stage. As mentioned before, melamine precondensates havebeen found to be particularly suitable for the second impregnatingstage.

Generally, it is desirable to submit the fibrous sheet material afterprimary impregnation to a stabilizing and, if desired, vulcanizingtreatment, for instance by heating, before carrying out the finalimpregnation by introducing the precondensates into the preimpregnatedfibrous sheet material and subsequent hardening. Alternatively, thefibrous material leaving the first impregnating stage may be onlylightly dried and submitted in this condition to the final impregnatingtreatment with synthetic resin precondensates. In the latter case, it isadvisable to use for the second stage impregnation emulsions,dispersions or solutions which contain the synthetic resin precondensatein a relatively high concentration. The impregnating products are thensubjected to a preferably intense drying and to a treatment, such as aheat treatment, which serves to harden the introduced precondensates.The hardening process may oe carried out in such a manner thatsimultaneously the vulcanizable filmstage -revulcanized v In thiscase,"vthe second stage impregnation may becarried out withfan emulsion,-dispersionorsolution containing, in addition to theffsynthetic resinprecondensates and the condensationcatalysts, also vulcanizing agentsand possible vvulcanization accelerators.

The second 'stage impregnation of'thelibrous sheet materialpreimpregn'ated with'lm-.forming binders can be carried out bysaturating the material throughout with tiret-emulsion, Idispersion orsolution of the syntheticresin precondensate followed by a suitablehardening step, if desired@ after removal of excess precondensate liquidby squeezing outU or the like. vuAlternatively, thek second inip'regrratingy step maybe so controlled that only one or both surfacelayers of the d brous sheet material are impregnated to a desireddepthwith the synthetic resin precoden'sate liquid, for instance, byspraying or spreading-tof thelat'ter upon one or bothsurfaces ofthesheet material. `This makes it possible to produce certain desiredsurface effects.

Finally, it has been found that in some cases it is advantageous tosubmit the fibrous sheet material into which, according to the presentinvention, synthetic resins have been introduced to an after-treatmentwith superheated steam, for instance in a drying room or under a pressor on drying cylinders. Such treatment with superheated steam may, ifdesired, be utilized for the hardening of the synthetic resin condensateintroduced into the fibrous material and/or for the vulcanization of thevu1- canizable binders, such as rubber.

Example 3 A fibrous fleece prepared and pre-stabilized by a unilateralsurface treatment according to Example 1 was through impregnated in afirst impregnating stage by passing it between a pair of rollers andpressing into the untreated surface thereof a stable owable foamobtained from an aqueous dispersion containing the following solidingredients:

Parts B. W. Butadiene-acrylonitrile polymer 100 Sodiumsulphonate(dispersing agent) 27 Sulphur 3 Active zincoxide 5 vuikazit P extra N(zinc sait of phenyliethyr dithiocarbaminic acid) 1 80 g. etherifledtrihydroxymethylmelamne (Lyolix MA) 15 g. diammonium-phosphate l5 g.dicyandiamide The impregnated sheet material was pre-dried at about 80C. and finally hardened for about ten minutes at 140 C. In amodification, pre-drying was omitted and the impregnated material wasdried and hardened by heating it for twenty minutes to about 140 C.

Example 4 A fiber eece was prepared, surface stabilized and throughimpregnated in a rst impregnating stage as described in Example 3, butin this case the foam used in the first impregnating stage was obtainedfrom an aqueous-*dispersion containing the? following'vsoxlid irl-#f fIn this.; case,- dryingM-and .hardeninglwere `effected by heating theimpregnated material for'about 21A 'minutesl to 165 Example 5 A surfacestabilized fiber eece was treated in a rst impregnating stage, asdescribed in Example 3, with a foam obtained from a dispersion of thefollowing composition:

Llquid Solid Parts Parts B. W. B. W.

Leguvol T (polyester resin) dis ersion 27.1 20. 25 Emulphor FFO (30%)(alkylnap thylpolyglycolether) solution 6 1.8 Benzeneperoxide(Hardener-BPO paste) 0. 72 0. 64 Nekal (alkyl-naphthalinesulphonate) 8 8Cobaltous chloride solution (20%) 0.9 0. 18 Softened water 48. l

After drying, vulcanization and washing, the material was treated in asecond impregnating stage with a solution containing per liter thefollowing solid ingredients:

g. etherilied hydroxymethylmelamine (Aerotex M3) 15 g. of a mixturecontaining isopropanolamine hydrochloride (UTX) 20 g. dicyandiamideAfter drying, the product was in this case hardened under a pressure of0.5 kg. per square centimeter at a temperature of C. It was found thatcomplete conversion of the synthetic resin precondensate to itsinsoluble state occurred in two to three seconds.

The process according to the present invention makes it possible toproduce porous sheet material which, due to the increased condensationof the fiber material, have a relatively high specific weight. The hand,the springiness and other properties are improved. Moreover, theproducts obtained accordingto the present invention are characterized byparticularly smooth surfaces, and high resistance to dry cleaningfluids.

We claim:

1. In the manufacture of porous sheet material similar to textile orleather and containing from about 25-65% by weight of rubber based onthe combined wei-gh-ts of fibers and rubber, wherein a fleece ofcardable polyposed fibers is impregnated with an aqueous dispersion of arubber and the impregnated ileece is thereafter dried to deposit therubberv primarily at the crossing points of the fibers, the improvementwhich comprises introducing intothe fibrous sheet material, in additionto the rubber, from 1 to 15 parts by weight per 100 parts by weight ofrubber solids of a water-soluble condensation product of formaldehydewith a member of the group consisting of ureas, melamines and phenols,and there- ..11 aftenconverting said condensation product' towaterinsoluble form.

2. The process of claim 1, wherein the condensation product is employedin an amount ranging from 2 to 6 parts by weight per 10() parts byweight of rubber solids.

3. The process of claim 1, wherein the condensation product is atleastpartly included in the aqueous dispersion of the rubber solids.

4. The process of claim 3, wherein the aqueous dispersion of rubbersolids and condensation product is applied as a foam. Y f i 5. Theprocess of claim 1, wherein the rubber solids have a high Defo value andthe condensation product is employed .in an amount ranging from 1 to 2parts by weight per 100 parts by weight of rubber solids.

6. The process of claim 1, wherein the rubber solids have a low Defovalue and the condensation product is employed in an amount ranging from6 to 8 parts by weight per 1100 parts byweight of rubber solids.

7. The process of claim 1,l wherein the condensation product is at leastpartly applied as an aqueous dispersion after drying of the sheetmaterial following depositing of the rubber solids.

12 8. The process of claim 1, wherein the-condensation product is awater-soluble melamine formaldehyde.`

9. The process of claim l, wherein the aqueous rubber dispersion alsocontains a vulcanizingagent and the sheet material is subjected tovulcanization prior to application ofthe water-soluble.condensationproduct.

References Cited in the le of this patent UNITED STATES PATENTS1,459,499 Brown et al June 19, 1923 1,766,817 Friedlan-der et al. June24, 1930 1,899,535 Teague Feb. 28, 1933 1,936,999 Teague Nov. 28, 19332,088,227 Battye July 27, 1937 2,267,316 Thompson et a1. Dec. 23, 19412,424,923 Edgar July 29, 1947 2,467,233 Rust Apr. l2, 1949 2,536,050Fluck Jan. 2, 1951 2,563,897 Wilson Aug. 14, 1951 2,716,617 Auestu Aug.30, 1955

1. IN THE MANUFACTURE OF POROUS SHEET MATERIAL SIMILAR TO TEXTILE ORLEATHER AND CONTAINING FROM ABOUT 25-65% BY WEIGHT OF RUBBER BASED ONTHE COMBINED WEIGHTS OF FIBERS AND RUBBER, WHEREIN A FLEECE OF CARDABLEPOLYPOSED FIBERS IS IMPREGNATED WITH AN AQUEOUS DISPERSION OF A RUBBERAND THE IMPREGNATED FLEECE IS THEREAFTER DRIED TO DEPOSIT THE RUBBERPRIMARILY AT THE CROSSING POINTS OF THE FIBERS, THE IMPROVEMENT WHICHCOMPRISES INTRODUCING INTO THE FIBROUS SHEET MATERIAL, IN ADDITION TOTHE RUBBER, FROM 1 TO 15 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OFRUBBER SOLIDS OF A WATER-SOLUBLE CONDENSATION PRODUCT OF FROMALDEHYDEWITH A MEMBER OF THE GROUP CONSISTING OF UREAS, MELAMINES AND PHENOLS,AND THEREAFTER CONVERTING SAID CONDENSATION PRODUCT TO WATERINSOLUBLEFORM.